IELp cells showing signs of recent high-affinity TCR signaling display increased expression of α₄β₇, whereas IELp cells lacking signs of high-affinity TCR signals are skewed toward expression of CD103. Thymocytes were analyzed for markers TCR signaling strength and the adhesion molecules α₄β₇ and CD103 to dissect the heterogeneity of the IELp (CD4^−/dullCD8^−/dullNK1.1⁻TCRβ⁺CD5⁺) population. (A) CD122⁻ and CD122⁺ IELp cells from the indicated mice were analyzed for expression of α₄β₇ and CD103. Data are representative of six individual experiments; WT (n = 6), 1KO (n = 6), BKO (n = 6). (B) Frequencies (left) and numbers (right) of α₄β₇- and CD103-expressing subpopulations of CD122⁺ IELps. Error bars indicate SEM. (C) GFP expression in DP, CD4SP, CD8SP, CD122⁻ IELp, and CD122⁺ IELp thymocyte populations from Nur77^GFP reporter mice. Data are representative of five individual experiments; n = 5. (D) IELp cells were analyzed for expression of GFP and CD122. GFP^hiCD122⁺ and GFP^loCD122⁺ thymocytes from Nur77^GFP mice were subsequently examined for expression of α₄β₇ and CD103 (right). Data are representative of five individual experiments; n = 5. (E) IELp cells were analyzed for expression of PD-1 and CD122 (left). PD-1⁺CD122⁺ and PD-1⁻CD122⁺ were examined for expression of α₄β₇ and CD103 (right). Data are representative of four individual experiments; n = 4.